Fully, completely (6)
I believe the answer is:
wholly
I believe this clue is a double definition.
'fully' is the first definition.
(thesaurus)
'completely' is the second definition.
(I know that completely can be written as wholly)
(Other definitions for wholly that I've seen before include "in every area" , "Without exception" , "in full?" , "One hundred per cent" , "Entirely, fully" .)